The present invention relates to a process for improving the charge state of a battery arrangement in a motor vehicle.
A process of the generic type is disclosed in German Patent Document DE-OS 23 50 494, in which the charge value of a battery charge system of a motor vehicle is raised for a specific time after a net discharge, the net discharge being measured, preferably by measuring if the generator is operating at full power. A disadvantage of this arrangement lies in the degree of expenditure required to implement it.
Furthermore, a German Publication Autoelektrik, Autoelektornik am Ottomotor/Bosch [Car electrics, car electronics in the spark ignition engine/Bosch]; First edition; Dussedlorf: published by VDI, 1987, pp. 36-45, ISBN 3-18-419106-0) discloses a process according to which the output voltage of a generator driven by the internal combustion engine, which varies due to fluctuations in the speed of rotation of an internal combustion engine, is controlled so that the output voltage does not exceed a specific threshold value. This specific threshold value is temperature-dependent such that according to an example described there an output voltage of approximately 14.9 V is obtained at an ambient temperature of 250.degree. K., and an output voltage of approximately 13.5 V at an ambient temperature of 370.degree. K. Between these two points, the specific threshold value changes with the ambient temperature in an essentially linear fashion. Compensation of the ambient temperature can be carried out by balancing resistors.
In a different exemplary embodiment of a controller it is shown that electronic compensation of the ambient temperature can be achieved, thereby obtaining a higher charging current for charging a vehicle battery at low ambient temperatures. At higher ambient temperatures, only a lower charging current is required so that the specific threshold value also assumes a lower value. A disadvantage of the known process resides in the fact that the degree of discharging of the vehicle battery is inadequately accounted for.
The object of the present invention is to provide an improved process for charging the vehicle battery in which the degree of the previous discharging of the vehicle battery is taken into account as far as possible.
This object is achieved according to the invention, in which the discharging of a vehicle battery after starting an internal combustion engine (which is severe in comparison with the rate of discharge associated with other operating states) is allowed for by a rapid and efficient recharging. That is, immediately after a starting process, at least under specific operating conditions, the threshold value of the generator output voltage is raised for a specific period so that, as a function of the specific operating conditions, a higher charge voltage may be present at the terminals of the vehicle battery than actually corresponds to the momentary operating conditions (particularly the ambient temperature) in accordance with the state of the art.
One advantage of the invention over the known state of the art is that the discharging of the vehicle battery during a starting process is taken into account.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.